<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>9.2</title>
	<script src="js/vue.js"></script>
	</head>
	<body>
		<div id="app"></div>
	</body>
	<script>
		var vm = new Vue({
			el: '#app',
			data: {
				km: 0,
				m: 0
			},
			methods: {
				kmtom: function(val){
					this.m = this.km *1000 ;
				},
				mtokm: function(val) {
					this.km = this.m/1000;
				}
			},
			watch: {
				km: 'kmtom',
				m: 'mtokm'
			}
		})
	</script>
</html>